Fuel cell separator with gasket and method for manufacturing the same

ABSTRACT

The present invention provides a fuel cell separator with a gasket manufactured by integrally forming a gasket on one side of a separator; independently injection molding a frame gasket on a frame such that a first airtight portion covers the entire surface of the frame to maintain the shape of the frame gasket and a second airtight portion projects upward and downward from both ends of the first airtight portion; and bringing the first airtight portion of the frame gasket into contact with the other side of the separator with the gasket formed on one side thereof. To create a fuel cell stack in certain embodiments, the invention stacks the second airtight portion of the frame gasket on another second airtight portion of an adjacent unit cell with a membrane-electrode assembly interposed therebetween.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of KoreanPatent Application No. 10-2010-0114717 filed Nov. 17, 2010, the entirecontents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present invention relates to a fuel cell separator with a gasket anda method for manufacturing the same. More particularly, it relates to afuel cell separator with a gasket which can further improveairtightness, electrical stability, and durability, and a method formanufacturing the same.

(b) Background Art

The configuration of a fuel cell stack may be described as follows withrespect to a unit cell. A membrane-electrode assembly (MEA) ispositioned in the center of each unit cell of the fuel cell stack. TheMEA comprises a polymer electrolyte membrane, through which hydrogenions (protons) are transported, and an electrode/catalyst layer such asan air electrode (cathode) and a fuel electrode (anode), in which anelectrochemical reaction between hydrogen and oxygen takes place,disposed on each of both sides of the polymer electrolyte membrane.

Moreover, a gas diffusion layer (GDL) and a gasket are sequentiallystacked on both sides of the MEA, where the cathode and the anode arelocated. A separator including flow fields for supplying fuel anddischarging water produced by the reaction is located on the outside ofthe GDL. After a plurality of unit cells are stacked together, an endplate for supporting the above-described components is connected to theoutermost ends of the fuel cell stack, thereby completing themanufacturing the fuel cell stack.

Therefore, at the anode of the fuel cell stack, hydrogen is dissociatedinto hydrogen ions (protons, H+) and electrons (e−) by an oxidationreaction of hydrogen. The hydrogen ions and electrons are transmitted tothe cathode through the electrolyte membrane and the separator,respectively. At the cathode, water is produced by the electrochemicalreaction in which the hydrogen ions and electrons transmitted from theanode and the oxygen in air participate and, at the same time,electrical energy is produced by the flow of electrons.

The separator (especially, a metal separator) of the fuel cell stackincludes flow fields formed by stamping a thin metal plate having athickness of about 0.1 mm to supply a reducing gas and an oxidizing gasto the fuel cell stack, supply coolant for cooling the fuel cell stack,and collect and transmit generated electricity. Therefore, the separatorshould have airtightness and liquid-tightness such that the reducinggas, the oxidizing gas, and the coolant are not mixed together.

Therefore, the gasket is applied to one side of the separator tomaintain the airtightness of the coolant and reactant gases (hydrogenand air) and, at the same time, support the gasket disposed on the otherside of the separator.

The gasket is integrally formed on both sides of a metal separator byinjection molding in terms of productivity during manufacturing of thefuel cell stack. An example of this is described with reference to FIG.1 and FIG. 2.

In particular, FIG. 1 is a cross-sectional view showing a conventionalmethod of integrally bonding a gasket 7 to a separator by injectionmolding. First, an adhesive is applied to an area, where the gasket 7 isto be formed, of the entire surface of a metal separator 1 (hereinafterreferred to as a separator).

Then, the separator 1 is loaded on the top of a lower mold 3 in such amanner that the separator 1 is positioned between an upper gasket groove2 a and a lower gasket groove 3 a, which are configured to fit the shapeof the gasket 7 in an upper mold 2 and the lower mold 3.

Subsequently, the upper mold 2 is moved to press and fix the edge of theseparator 1, and then a gasket material is injected into the top andbottom of the separator 1 to integrally mold and bond a gas side gasket5 and a cooling side gasket 6 to both sides of the separator 1.

FIG. 2 is a plan view and a cross-sectional view showing the structureof the conventional metal separator 1 integrated with the gasket 7 byinjection molding. As shown in the figure, the gasket 7 is integrallyformed on the edge of the metal separator 1 and on the periphery ofmanifolds. The gasket 7 comprises the gas side gasket 5 integrallyformed on the top of the metal separator 1 and maintaining theairtightness of reactant gas (hydrogen or air) and the cooling sidegasket 6 integrally formed on the bottom of the metal separator 1 andmaintaining the airtightness of coolant.

As such, the gasket 7 formed on the separator serves as a basis fordefining each unit cell of the fuel cell stack and seals hydrogen,coolant, and air flow fields, respectively, formed on the surface of theseparator 1.

While the above-described method of forming the gasket 7 on both sidesof the separator 1 by injection molding can manufacture the fuel cellstack in a simple manner, the following problems are encountered duringinjection molding of the gasket 7, which will be described withreference to FIGS. 3 and 4.

FIG. 3 is a cross-sectional view showing the occurrence of deformationand contamination of the separator 1 during injection molding of thegasket 7.

The structures and thicknesses of the gas side gasket 5 and the coolingside gasket 6 formed on both sides of the separator 1 are different fromeach other, and thus when the gasket material is injected on both sidesof the separator 1 formed of a thin plate having a thickness of about0.1 mm, the midsection of the separator 1 may be bent downward due to apressure difference between the gasket materials being flowed throughboth sides of the separator 1.

For example, when the gasket material is simultaneously injected intothe upper gasket groove 2 a formed in the upper mold 2 and the lowergasket groove 3 a formed in the lower mold 3, the amount of the gasketmaterial filled in the upper gasket groove 2 a having a large thicknessis greater than that of the gasket material filled in the lower gasketgroove 3 a having a small thickness, and thus a pressure differencebetween the gasket materials filled in the upper gasket groove 2 a andthe lower gasket groove 3 a occurs. As a result, the midsection of theseparator 1 is bent downward due to the pressure difference.

Moreover, a non-filled portion may occur due to a difference in flowrate between the gasket materials being flowed through both sides of theseparator 1. Otherwise, the gasket material leaks from the upper andlower molds 2 and 3, which results in the formation of burrs.

For example, when the gasket material is injected into the gasketgrooves 2 a and 3 a at the same pressure, the flow rate of the gasketmaterial being flowed through the upper gasket grooves 2 a is lower thanthat of the gasket material being flowed through the lower gasket groove3 a, which results in the occurrence of the non-filled portion.

Moreover, when the pressure of the gasket material being flowed throughthe upper gasket groove 2 a is higher than the pressure applied to theedge of the separator 1, into which no gasket material is injected, thegasket material leaks from a gap between the upper and lower molds 2 and3 and is then solidified, which results in the formation of the burrs.

In addition, when the gasket material is introduced through the gapbetween the upper and lower molds 2 and 3, it contaminates the surfaceof the separator 1, which increases the contact resistance of theseparator 1, thereby deteriorating the performance of the fuel cellstack.

When the burrs are present in the flow fields of the separator having aconcave-convex structure, the removal of the burrs cannot be automatedusing a tool or die cutter, and thus the removal of the burrs should beperformed manually.

FIG. 4 is a cross-sectional view showing the occurrence of short circuitand corrosion in a recess of a conventional separator integrated with agasket.

It can be seen from FIG. 4 that the gasket 7 is not formed on the edgeof the separator 1, and the metal surface of this edge of the separator1 on which the gasket 7 is not formed is always exposed to the outside.

The reason that the gasket 7 is not formed on the edge of the separator1 is that when the gasket 7 is integrally formed on the separator 1, theedge of the separator 1 is in contact with the upper and lower molds 2and 3 and held thereby.

Of course, even though the gasket 7 is not formed on the edge of theseparator 1, it has no significant effect on the airtightnessperformance.

However, the edge of the separator 1 is a dead zone which is not relatedto the performance of the fuel cell. When the area of the edge of theseparator 1 is increased to reduce the deformation of the separator 1,which is caused by the pressure difference between the gasket materialsbeing flowed through both sides of the separator 1, the power density ofthe fuel cell stack may be reduced.

In particular, a recess formed in an empty space between the edges ofthe separators 1 is most likely to be exposed to high temperature andhigh humidity conditions, which often occur during operation of the fuelcell stack, and in this case, condensed water is formed in the recessformed in the empty space between the edges of the separators 1.

As a result, the condensed water flows through the unit cells to form anelectrical path, which results in the occurrence of short circuitbetween the unit cells. Moreover, the surface of the separator 1 iscorroded by the condensed water, which reduces the durability of theseparator 1.

Reference numeral 8 in FIG. 4 denotes a membrane-electrode assembly(MEA).

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE DISCLOSURE

The present invention provides a fuel cell separator with a gasket and amethod for manufacturing the same, which can solve problems such asdeformation, contamination, etc., of the separator, which are caused bya difference in injection pressure applied to both sides of theseparator when a gasket material is simultaneously injected on bothsides of the separator, by injection molding the gasket material only onone side of the separator.

Moreover, the present invention provides a fuel cell separator with agasket and a method for manufacturing the same, which can improveairtightness of the separator by providing a projection at both ends ofa gasket frame including a frame mounted therein to cover and seal arecess formed between the edges of the separators and can solve problemssuch as insulation and corrosion of a fuel cell stack by employing aseparator to which a gasket frame is applied during manufacturing of thefuel cell stack.

In one aspect, the present invention provides a fuel cell separator witha gasket, the fuel cell separator comprising: a gasket integrally formedon one side of a separator and maintaining airtightness; and a framegasket configured independently from the separator, including a firstairtight portion being in contact with the other side of the separator,and maintaining the airtightness.

In one embodiment, the first airtight portion of the frame gasketcomprises a frame mounted therein to maintain the shape of the framegasket.

In another embodiment, the frame gasket comprises a second airtightportion projecting upward and downward from both ends of the firstairtight portion to seal the separator and the gasket and further securethe airtightness.

In still another embodiment, the first airtight portion is in contactwith the edge of the separator on a cooling side and the periphery ofmanifolds to maintain the airtightness.

In another aspect, the present invention provides a method ofmanufacturing a fuel cell separator with a gasket, the methodcomprising: integrally forming a gasket on one side of a separator;injection molding a frame gasket on a frame such that a first airtightportion covers the entire surface of the frame to maintain the shape ofthe frame gasket and a second airtight portion projects upward anddownward from both ends of the first airtight portion, the injectionmolding being performed independently from the formation of the gasket;and bringing the first airtight portion of the frame gasket into contactwith the other side of the separator with the gasket formed on one sidethereof and stacking the second airtight portion of the frame gasket onanother second airtight portion of an adjacent unit cell with amembrane-electrode assembly interposed therebetween.

In one embodiment, the gasket is integrally formed on one side of theseparator by injection molding a gasket material.

In another embodiment, the gasket is integrally formed on one side ofthe separator by applying a liquid gasket.

In still another embodiment, the gasket is integrally formed on one sideof the separator by bonding a solid gasket using an adhesive.

In yet another embodiment, the first airtight portion covers the entiresurface of the frame by an upper projection and a lower projection,which are integrally formed in an upper mold and a lower mold,respectively.

Other aspects and preferred embodiments of the invention are discussedhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated the accompanying drawings which are givenhereinbelow by way of illustration only, and thus are not limitative ofthe present invention, and wherein:

FIG. 1 is a cross-sectional view showing a generally conventional methodof integrally bonding a gasket to a separator by injection molding;

FIG. 2 is a plan view and a cross-sectional view showing the structureof a generally conventional metal separator integrated with a gasket byinjection molding;

FIG. 3 is a cross-sectional view showing the occurrence of deformationand contamination of a separator during injection molding of a gasket;

FIG. 4 is a cross-sectional view showing the occurrence of short circuitand corrosion in a recess of a conventional separator integrated with agasket;

FIG. 5 is a schematic diagram showing a method for manufacturing aseparator with a gasket injection-molded on one side of the separator inaccordance with an illustrative embodiment of the present invention;

FIG. 6 is a schematic diagram showing a method for manufacturing a framegasket in accordance with an illustrative embodiment of the presentinvention;

FIG. 7 is a plan view and a cross-sectional view showing a separatorassembly in accordance with an illustrative embodiment of the presentinvention;

FIG. 8 is a cross-sectional view showing the structure of a separatorassembly in a unit cell in accordance with an illustrative embodiment ofthe present invention; and

FIG. 9 is a cross-sectional view showing the structure of a fuel cellstack in accordance with an illustrative embodiment of the presentinvention.

Reference numerals set forth in the Drawings includes reference to thefollowing elements as further discussed below:

10: separator;

11: first mold;

12: upper mold;

12 a: upper gasket molding groove;

13: lower mold;

13 a: separator receiving groove;

14: gas side gasket;

20: frame gasket;

21: frame;

22: first airtight portion;

23: second airtight portion;

24: second mold;

25: upper mold;

25 a: upper receiving groove;

25 b: upper intermediate groove;

25 c: upper projection;

26: lower mold;

26 a: lower receiving groove;

26 b: lower intermediate groove; and

26 c: lower projection.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the present invention asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes will be determined in part by theparticular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter reference will now be made in detail to various embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings and described below. While the invention will bedescribed in conjunction with exemplary embodiments, it will beunderstood that present description is not intended to limit theinvention to those exemplary embodiments. On the contrary, the inventionis intended to cover not only the exemplary embodiments, but alsovarious alternatives, modifications, equivalents and other embodiments,which may be included within the spirit and scope of the invention asdefined by the appended claims.

Also, it is understood that the term “vehicle” or “vehicular” or othersimilar term as used herein is inclusive of motor vehicles in generalsuch as passenger automobiles including sports utility vehicles (SUV),buses, trucks, various commercial vehicles, watercraft including avariety of boats and ships, aircraft, and the like, and includes hybridvehicles, electric vehicles, plug-in hybrid electric vehicles,hydrogen-powered vehicles and other alternative fuel vehicles (e.g.fuels derived from resources other than petroleum). As referred toherein, a hybrid vehicle is a vehicle that has two or more sources ofpower, for example both gasoline-powered and electric-powered vehicles.

FIG. 5 is a schematic diagram showing a method for manufacturing aseparator with a gasket injection-molded on one side of the separator inaccordance with an illustrative embodiment of the present invention.

The present invention provides a fuel cell separator 10 with a gasketinjection-molded on one surface thereof and a method for manufacturingthe same.

The fuel cell separator 10 with the gasket for maintaining theairtightness is a metal separator, for example.

The method of manufacturing the fuel cell separator 10 with the gasketinjection-molded on one surface thereof will be described below.

First, an adhesive is applied to the top of the separator 10, on whichthe gasket is to be injection-molded, e.g., by screening printing. Here,the adhesive applied to the surface of the separator 10 may be the samematerial as a gasket material, and preferably may be fluorine rubber orsilicon rubber primer.

The separator 10 to which the adhesive is applied is loaded in a mold 11(hereinafter referred to as a first mold) for injection molding theseparator 10. The first mold 11 comprises an upper mold 12 and a lowermold 13. As an example, the upper mold 12 may be used as a movable moldand the lower mold 13 may be used as a fixed mold. An upper gasketmolding groove 12 a for forming a gas side gasket 14 is provided in theupper mold 12. Moreover, a separator receiving groove 13 a is providedin the lower mold 13, and the bottom of the separator receiving groove13 a is a flat surface for supporting the bottom of the separator 10.The separator 10 to which the adhesive is applied is inserted into theseparator receiving groove 13 a of the lower mold 13. Then, the uppermold 12 is moved to close the lower mold 13. Here, the edge of theseparator 10 is sandwiched between the upper mold 12 and the lower mold13 by the pressing force of the upper mold 12. Finally, the gasketmaterial is injected into the upper gasket molding groove 12 a formed inthe upper mold 12 to form the gas side gasket 14, and then the uppermold 12 is opened to remove the injection-molded gas side gasket 14 fromthe first mold 11, thus completing the manufacturing of the separator 10with the gasket injection-molded on one surface thereof.

The gas side gasket 14 is injection-molded and integrally bonded to thetop of the separator 10 manufactured by the above-described method.Here, the gas side gasket 14 is integrally bonded to the edge of a fuelelectrode separator 10 a or an air electrode separator 10 b and to theperiphery of manifolds to maintain the airtightness of the separator 10such that hydrogen and oxygen introduced through the manifolds aresupplied through flow fields of the separator 10.

Moreover, a frame gasket 20 including a projection formed at both endsis injection-molded, separately from the manufacturing of the separator10 with the gas side gasket 14 injection-molded on one surface thereof.

While the gas side gasket 14 is formed by injection molding, a liquidgasket may be applied to one side of the separator 10 or a solid gasketmay be bonded to one side of the separator 10 using an adhesive, therebyintegrally forming the gas side gasket 14 on one side of the separator10.

Next, a method for manufacturing the frame gasket 20 in accordance witha preferred embodiment of the present invention will be described withreference to the accompanying drawings.

FIG. 6 is a schematic diagram showing a method for manufacturing a framegasket in accordance with an illustrative embodiment of the presentinvention, and FIG. 7 is a plan view and a cross-sectional view showinga separator assembly in accordance with an illustrative embodiment ofthe present invention.

First, a frame 21, which will be inserted into the frame gasket 20 tomaintain the shape of the frame gasket 20, is formed. The frame 21 hasthe same shape as the gas side gasket 14 and is formed of the samematerial as the separator 10. The frame 21 may be formed of a polymersuch as plastic or a glass fiber material in terms of weight and cost.However, the frame 21 should be formed of a material that has a certaindegree of stiffness to maintain the shape of the gasket during theautomatic process of manufacturing the fuel cell stack.

A mold 24 (hereinafter referred to as a second mold) for injectionmolding the frame gasket 20 comprises an upper mold 25 including a pairof upper receiving grooves 25 a formed at both sides thereof and a lowermold 26 including a pair of lower receiving grooves 26 a formed at bothsides thereof. The upper mold 25 may be used as a movable mold and thelower mold 26 may be used as a fixed mold. The upper receiving grooves25 a are arranged horizontally at a predetermined interval in the uppermold 25, and an upper intermediate groove 25 b is provided between theupper receiving grooves 25 a at a level lower than the tops of the upperreceiving grooves 25 a. Here, both sides of each upper receiving groove25 a are tapered in such a manner that the cross-sectional area of eachupper receiving groove 25 a increases downward such that the moldedproduct can be easily removed from the mold.

Moreover, an upper projection 25 c is formed to project downward fromthe center of the bottom of the upper mold 25 to guide the frame 21 tobe located in the center of the frame gasket 20. In other words, theupper projection 25 c is fixed to the bottom of the upper mold 25 tosupport the top center of the frame 21 such that the frame 21 isinserted between the upper intermediate groove 25 b and a lowerintermediate groove 26 b, which will be described later, and is notmoved during injection of the gasket material.

The lower receiving grooves 26 a are arranged to correspond to the upperreceiving grooves 25 a in the lower mold 26, and the lower intermediategroove 26 b is provided between the lower receiving grooves 26 a at alevel higher than the bottoms of the lower receiving grooves 26 a. Here,both sides of each lower receiving groove 26 a are tapered in such amanner that the cross-sectional area of each lower receiving groove 26 aincreases upward such that the molded product can be easily removed fromthe mold.

Moreover, a lower projection 26 c is formed to project upward from thecenter of the top of the lower mold 26 to guide the frame 21 to belocated in the center of the frame gasket 20. In other words, the lowerprojection 26 c is fixed to the top of the lower mold 26 to support thebottom center of the frame 21 such that the frame 21 is inserted betweenthe upper intermediate groove 25 b and the lower intermediate groove 26b and is not moved during injection of the gasket material.

Each of the upper projection 25 c and the lower projection 26 c has alength such that the top and bottom of the frame 21 can besimultaneously fixed by the upper projection 25 c and the lowerprojection 26 c when the upper mold 25 and the lower mold 26 are closed.Moreover, the distance between the upper projection 25 c and the lowerprojection 26 c should be the same as or smaller than the thickness ofthe frame 21 to firmly fix the frame 21.

Then, the frame 21 is loaded in the second mold 24 having theabove-described structure. During loading of the frame 21, the frame 21is placed on the lower projection 26 c provided between the lowerreceiving grooves 26 a of the lower mold 26. Subsequently, the uppermold 25 is moved downward to be placed on the lower mold 26. Here, theupper projection 25 c of the upper mold 25 presses the top of the frame21 placed on the lower projection 26 c of the lower mold 26 by theclosing force of the upper mold 25 to fix the frame 21.

After the frame 21 is fixed, the gasket material is injected throughinlets of the upper mold 25 and the lower mold 26 to form the framegasket 20, and then the upper mold 25 is opened to remove theinjection-molded frame gasket 20 from the second mold 24, thuscompleting the manufacturing of the frame gasket 20 with the projectionformed at both ends thereof.

The frame gasket 20 formed by the above-described method comprises theframe 21 serving as a frame, a first airtight portion 22 covering theframe 21 and being in contact with the cooling side of the separator 10,and a second airtight portion 23 projecting from both ends of the firstairtight portion 22 in the thickness direction of the gasket.

The first airtight portion 22 of the frame gasket 20 is located betweenthe fuel electrode separator 10 a and the air electrode separator 10 b(i.e., on opposing sides of the first airtight portion), is in contactwith the cooling side of the separator 10 by the fastening force of thefuel cell stack to maintain the airtightness, and supports the gas sidegasket 14.

The second airtight portion 23 projects from both ends of the firstairtight portion 22 in the stacking direction of the fuel cell stack(i.e., in the up and down direction) to cover the separator 10 and thegas side gasket 14 and seal the recess formed between the edges of theseparators 10, thus further maintaining the airtightness of the fuelcell stack.

FIG. 8 is a cross-sectional view showing the structure of a separatorassembly in a unit cell in accordance with an illustrative embodiment ofthe present invention, and FIG. 9 is a cross-sectional view showing thestructure of a fuel cell stack in accordance with an illustrativeembodiment of the present invention. In one embodiment, the fuel cellstack is a vehicle fuel cell stack for use in powering vehicles (e.g.,hybrid vehicles). Other uses of fuel cell stacks, however, may alsobenefit from the particular embodiments described herein.

As shown in the figures, the fuel cell stack comprises a plurality ofunit cells, in which the air electrode separator 10 b including an airelectrode gasket injection-molded on the bottom thereof, the firstairtight portion 22 of the frame gasket 20, the fuel electrode separator10 a including a fuel electrode gasket injection-molded on the topthereof, and a membrane-electrode assembly (MEA) 8 are sequentiallystacked, the plurality of unit cells being repeatedly stacked.

The second airtight portion 23 of the gasket frame 20 is in contact withanother second airtight portion 23 of an adjacent unit cell and iscompressed by the fastening force of the fuel cell stack. Here, thethickness t₂ of the second airtight portion 23 projection from the topof the first airtight portion 22 is the sum of the thickness t₁ of thegas side gasket 14 and the thickness t of the separator 10 (t₂=t₁+t).

The operation and effect of the fuel cell separator with the gaskethaving the above-described configuration will be described below.

According to the present invention, the gasket material is injected onlyon one side of the separator 10, differently from the conventionalseparator with the gasket integrally formed on both sides thereof. Whenthe gasket material is injected only on one side of the separator 10according to the present invention, the other side of the separator 10is supported by the flat surface of the mold, and thus it is possible tosolve the problem of deformation of the separator 10, which is causedwhen the gasket material is simultaneously injected on both sides of theseparator.

Moreover, when the gasket material is injected only on one side of theseparator 10, it is possible to solve the problem that the gasketmaterial is introduced through a gap between the upper and lower molds,which is caused by a pressure difference between both sides of theconventional separator in which the gasket material is simultaneouslyinjected on both sides of the separator, and thus it is possible toprevent the contamination of the separator.

When the gasket material is injected on the frame 21, burrs may beformed on both sides of the second airtight portion 23. However, theburrs are different from those formed when the gasket material isinjected on both sides of the separator, and the gasket material is notformed at the flow fields of the separator 10 having a concave-convexstructure. The thus formed burrs project from both sides of the secondairtight portion 23, and thus the removal of the burrs can be automatedusing a burr removal tool or die cutter.

The second airtight portion 23 of the frame gasket 20 projects upwardand downward from both ends of the first airtight portion 22 and isstacked alternately with the MEA 8 to cover and seal the recess formedbetween the edges of the separators 10, thus insulating the unit cellsfrom each other. As a result, the electrical stability and airtightnesscan be improved.

For example, the second airtight portion 23 seals the recess (i.e.,empty space) formed between the edges of the separators 10 such that thecondensed water formed in the recess is prevented from being moved tothe other unit cells, and thus it is possible to prevent the occurrenceof short circuit and corrosion, which are caused when the condensedwater formed in the recess is exposed to the outside, and improve thedurability of the separator 10.

The both sides of the second airtight portion 23 are tapered in such amanner that the cross-sectional area thereof decreases upward anddownward with respect to the horizontal centerline of the frame 21, andthus it is possible to reduce the flow resistance of reactant gasesintroduced through the manifolds.

While the frame gasket 20 is uses as the cooling side gasket in theabove embodiment of the present invention, it can be used as the gasside gasket 14.

Typically, the gasket is formed of expensive fluorine materials havingexcellent chemical resistance to resist the acidic environments of thereaction surface due to the nature of the fuel cell. However, when thecooling side gasket which is not required to have excellent chemicalresistance is used instead of the frame gasket 20, it is possible to useless expensive materials such as silicon or EDPM.

As described above, the fuel cell separator with the gasket and themethod for manufacturing the same according to the present inventionhave the following advantages.

1. As the gasket material is injected only one side of the separator,the other side of the separator is supported by the flat surface of themold, and thus it is possible to alleviate the problem of deformation ofthe separator, which is caused when the gasket material issimultaneously injected on both sides of the separator.

2. As the gasket material is injected only on one side of the separator,it is possible to alleviate the problem that the gasket material isintroduced through a gap between the upper and lower molds, which iscaused by a pressure difference between both sides of the conventionalseparator in which the gasket material is simultaneously injected onboth sides of the separator, and thus it is possible to prevent thecontamination of the separator.

3. When the gasket material is injected on the frame, burrs may beformed on both sides of the second airtight portion. However, the burrsare different from those formed when the gasket material is injected onboth sides of the separator, and the gasket material is not formed atthe flow fields of the separator having a concave-convex structure. Thethus formed burrs project from both sides of the second airtightportion, and thus the removal of the burrs can be automated using a burrremoval tool or die cutter.

4. The second airtight portion of the frame gasket projects upward anddownward from both ends of the first airtight portion and is stackedalternately with the MEA to cover and seal the recess formed between theedges of the separators, thus insulating the unit cells from each other.As a result, the electrical stability and airtightness can be improved.

5. The second airtight portion seals the recess (i.e., empty space)formed between the edges of the separators such that the condensed waterformed in the recess is prevented from being moved to the other unitcells, and thus it is possible to prevent the occurrence of shortcircuit and corrosion, which are caused when the condensed water formedin the recess is exposed to the outside, and improve the durability ofthe separator.

6. The both sides of the second airtight portion are illustrativelytapered in such a manner that the cross-sectional area thereof decreasesupward and downward with respect to the horizontal centerline of theframe, and thus it is possible to reduce the flow resistance of reactantgases introduced through the manifolds.

The invention has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated by those skilled inthe art that changes may be made in these embodiments without departingfrom the principles and spirit of the invention, the scope of which isdefined in the appended claims and their equivalents.

1. An apparatus, comprising: a fuel cell separator; a gasket integrallyformed on a first side of the separator, the gasket being airtight withthe separator; and a frame gasket created independently from theseparator, the frame gasket having a first airtight portion in airtightcontact with a second side of the separator.
 2. The apparatus of claim1, wherein the first airtight portion of the frame gasket comprises aframe mounted therein to maintain a shape of the frame gasket.
 3. Theapparatus of claim 2, wherein the frame gasket comprises a secondairtight portion projecting upward and downward from both ends of thefirst airtight portion.
 4. The apparatus of claim 2, wherein the firstairtight portion is in airtight contact with an edge of the separator ona cooling side of the separator and in airtight contact with a peripheryof manifolds of the separator.
 5. The apparatus of claim 1, wherein theframe gasket comprises a second airtight portion projecting upward anddownward from both ends of the first airtight portion.
 6. The apparatusof claim 1, wherein the first airtight portion is in airtight contactwith an edge of the separator on a cooling side of the separator and inairtight contact with a periphery of manifolds of the separator.
 7. Theapparatus of claim 1, further comprising: a second fuel cell separatorand second gasket integrally formed on a first side of the secondseparator, wherein an opposing side of the first airtight portion of theframe gasket is in airtight contact with a second side of the secondseparator.
 8. A method for manufacturing a fuel cell separator with agasket, the method comprising: integrally forming a gasket on a firstside of a fuel cell separator; injection molding a frame gasket on aframe such that a first airtight portion of the frame gasketsubstantially covers a surface of the frame to maintain the shape of theframe gasket and a second airtight portion of the frame gasket projectsupward and downward from both ends of the first airtight portion, theinjection molding being performed independently from the formation ofthe gasket; and bringing the first airtight portion of the frame gasketinto contact with a second side of the separator with the gasket formedon the first side thereof.
 9. The method of claim 8, wherein the framegasket is part of a unit cell, the method further comprising: stackingthe second airtight portion of the frame gasket on another secondairtight portion of an adjacent unit cell with a membrane-electrodeassembly interposed therebetween.
 10. The method of claim 8, wherein thegasket is integrally formed on the first side of the separator byinjection molding a gasket material.
 11. The method of claim 8, whereinthe gasket is integrally formed on the first side of the separator byapplying a liquid gasket.
 12. The method of claim 8, wherein the gasketis integrally formed on the first side of the separator by bonding asolid gasket using an adhesive.
 13. The method of claim 8, wherein thefirst airtight portion covers the entire surface of the frame except forwhere an upper projection and a lower projection are integrally formedin an upper mold and a lower mold for the injection molding,respectively.
 14. A fuel cell stack, comprising: a plurality of fuelcell separators, each separator having an airtight gasket integrallyformed on a first side thereof; a plurality of frame gaskets createdindependently from the separators, each frame gasket having a firstairtight portion, the first airtight portion having opposing sides eachin airtight contact with a second side of a respective separator, eachframe gasket also having a second airtight portion projecting upward anddownward from both ends of the first airtight portion; and a pluralityof membrane-electrode assemblies, wherein the second airtight portion ofthe frame gaskets are stacked on another second airtight portion of anadjacent unit cell with one of the membrane-electrode assembliesinterposed therebetween.
 15. The fuel cell stack of claim 14, whereinthe fuel cell stack is a vehicle fuel cell stack.